1. Field of the Invention
This invention relates to a central office telephone switching system. More particularly, this invention relates to methods of and apparatus for monitoring telephone calls within a central office telephone switching system in such a way as to efficiently utilize the system.
2. Technical Consideration and Prior Art
Generally, when a telephone subscriber has finished a call he replaces his handset which indicates to a central office telephone switching system that this subscriber's call must be released within the system.
Heretofore, many central office switching systems have been able to terminate only one call at a time. Since switching systems must be designed to handle the volume of telephone calls generated during periods of peak telephone activity, it is necessary to provide sufficient switching capacity to accommodate a larger number of terminations. This capacity is not utilized during periods of low telephone activity so it is, in effect, wasted during those times. Furthermore, the additional capacity necessary for periods of peak activity is expensive to provide and maintain and consequently results in higher subscriber costs.
The central office switching systems with which the instant invention is concerned are in essence divided in half with two substantially identical switching circuits interconnected with one another. Each half of the circuit has a separate group of line units associated therewith which are connected to local telephones. Also connected to the circuit are outgoing trunks which transmit calls from the central office switching system to other remote central office systems. According to the teachings of the prior art, telephone calls terminated in such a central office were terminated one at a time in spite of the existence of separate number translator and code translator circuits. The inventor of the instant invention realized that the capacity of the system could be drastically increased if a way could be found to utilize both halves of the system so as to terminate two calls simultaneously.
Since there are more telephone calls terminated during periods of peak telephone traffic, there are more telephone calls available to the system for termination. Consequently, the system always has a large selection of calls during peak periods which can be in some way matched for simultaneous termination. Keeping in mind that there are local calls and trunk calls made by the system and that subscriber telephones are grouped in separate line units, there are different types of calls which may be terminated during periods of peak traffic. Since the system cannot terminate two similar calls simultaneously, the inventor of the instant invention has modified both the system and the use of the system to take advantage of the diversity of calls therewithin so as to terminate two calls simultaneously.
In accordance with the principles of the instant invention, two calls can be terminated by the central office simultaneously provided one call is a local call and the second call is a trunk call and further provided that the calls originated in separate line units or rather separate halves of the central office switching system.